Lindsay LohanMy Brakes Failed!!!

6/10/2012 12:30 PM PDT

Lindsay Lohan -- My Brakes Failed!!!

EXCLUSIVE

Lindsay Lohan is now telling friends the brakes on her rented Porsche DIDN'T WORK and that's why she slammed into the back of an 18-wheeler ... TMZ has learned.

As TMZ first reported, in the moments following the accident, Lindsay claimed the semi-truck cut her off ... and that is what caused the accident. The driver of the truck told TMZ that was not the case and has witnesses to back up his tale.

According to our sources, Lindsay is sticking with the "truck cut me off!!!" story, but with a twist ... she claims she slammed on the brakes ... but nothing. And get this ... somehow Lindsay says she was told the brakes on the rental were replaced two days before the crash.

Lindsay is telling people she feels lucky to be alive, having only suffered cuts and bruises ... no serious injuries.

Considering her driving history, one of these days ... well, let's just say she needs a driver.